CIE A Level Physics
CIE A Level Physics Astronomy and Cosmology Exam Questions
Free CIE A Level Physics exam questions for Astronomy and Cosmology, with a mark scheme for every pack. Covers standard candles, luminosity, radiant flux intensity, Wien's displacement law, Stefan-Boltzmann law, stellar radii, redshift and Hubble's law.
Astronomy and Cosmology exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
StemUp mark scheme flashcards
A-Level Physics Flashcards for 2027 Onwards
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Then test yourself with the questions on this page.
From £10.99View flashcards
About CIE A Level Physics Astronomy and Cosmology
Astronomy and cosmology is Topic 25 of the Cambridge International AS & A Level Physics (9702) syllabus. It explains how astronomers measure distances using standard candles, how luminosity and radiant flux intensity are related by the inverse square law, and how Wien's displacement law and the Stefan-Boltzmann law are combined to estimate the radius of a star. The final part covers redshift, Hubble's law and how they support the Big Bang theory. It links with Waves (Doppler effect) and Quantum physics. Examiners often ask you to find a star's radius or a galaxy's distance from data.
What you need to know
- Standard candles A standard candle is an object of known luminosity, such as a Cepheid variable or a type Ia supernova, so its distance can be found from its measured flux.
- Luminosity and flux Luminosity L is the total power emitted by a star. Radiant flux intensity F = L/(4πd^2), the power per unit area received at distance d.
- Wien's displacement law λmax ∝ 1/T, so hotter stars emit peak radiation at shorter wavelengths. λmaxT = constant (about 2.9 × 10^-3 m K).
- Stefan-Boltzmann law L = 4πσr^2T^4, where σ = 5.67 × 10^-8 W m^-2 K^-4. Combined with Wien's law to estimate a star's radius.
- Redshift Light from distant galaxies is shifted to longer wavelengths. For speeds much less than c: Δλ/λ ≈ Δf/f ≈ v/c.
- Hubble's law and the Big Bang Recession speed is proportional to distance, v = H0d. This shows the universe is expanding and is consistent with the Big Bang theory.
Common mistakes in Astronomy and Cosmology
- Using d instead of d^2 in F = L/(4πd^2).
- Using temperature in °C in Wien's or Stefan's law. Use kelvin.
- Forgetting to raise T to the fourth power, or using diameter instead of radius in L = 4πσr^2T^4.
- Saying redshift shows galaxies moving through space away from Earth at the centre. It shows space itself expanding, with all distant galaxies receding from each other.
- Mixing H0 units. Convert km s^-1 Mpc^-1 to s^-1 when finding distance in metres.
Try three Astronomy and Cosmology exam-style questions
1. The Sun's luminosity is 3.85 × 10^26 W and its distance from Earth is 1.50 × 10^11 m. Calculate the radiant flux intensity at Earth. (2 marks)
Show the mark scheme answer
F = L/(4πd^2) = 3.85 × 10^26/(4π × (1.50 × 10^11)^2); F = 1.36 × 10^3 W m^-2.
2. A star has surface temperature 5800 K. Calculate the wavelength at which its emission peaks. Take λmaxT = 2.9 × 10^-3 m K. (1 mark)
Show the mark scheme answer
λmax = 2.9 × 10^-3/5800 = 5.0 × 10^-7 m.
3. A galaxy shows a redshift Δλ/λ = 0.050. Taking H0 = 2.2 × 10^-18 s^-1, calculate its recession speed and distance. (3 marks)
Show the mark scheme answer
v = 0.050 × 3.00 × 10^8 = 1.5 × 10^7 m s^-1; d = v/H0 = 1.5 × 10^7/2.2 × 10^-18; d = 6.8 × 10^24 m.
Astronomy and Cosmology FAQs
What does Cambridge AS & A Level Physics Astronomy and cosmology cover?
It covers standard candles, luminosity and radiant flux intensity, Wien's displacement law, the Stefan-Boltzmann law, stellar radii, redshift, Hubble's law and the Big Bang theory.
Which paper is Astronomy and cosmology examined in?
It is an A Level topic assessed in Paper 4 (A Level Structured Questions).
How do I calculate the radius of a star?
Use Wien's law to find the surface temperature from λmax, find luminosity from flux and distance using F = L/(4πd^2), then rearrange L = 4πσr^2T^4 for r.
